Magnetron



Dec. 30, 1947. R. c. RETHERF/ORD 2,433,481

MAGNETRON Filed July 1,1943

'I I M il l I Z5 Z' ATTORNEY Patented Dec. 30, 1947 iran sr-Arss. PATENT crm;

to E-'Westinghouse Electric Corporation,

East

1 Pittsburgh, Pa., a corporation of Pennsylvania Application-July 1, 1943, Serial No. 492,985

14 lClaims. (Cl. Z50-27.5)

This inventionl relatestdmagnetrons and is moreparticularly directed to provision of means for tuning a magnetron to desired Wave-length.

One of the seriousdeiiciencies oimagnetrons has been .the inability'totunethe same to aldeflnite wave-length after assembly. Even with exercise of greatest possibleprecision of fabrication, the output waveflength has beenfound to varyin differentmagnetrons .intended to. be identical.

, This necessitates accuratetestingand calibration of each, magnetron' .and-.selection from .those tested of oneshaving the desired wave-length for a particulaiiuse,orinstallation.. Production of ,magnetrons for aA denite wave-length. is. there- `iore prolonged bythe unavoidable inclusion oi in use by the operator.

Al further object ofl theinvention 'is to'obtain a structure wherein wave-length tuning- Amay be effected` over a considerablerange.

Yet another object of the invention Ais to-promote more rapid manufacture by requiring-less :accuracy of `cathodemountingy with respect to .concentricity with the anode.

, More speciiically, anobject of the invention `is to obtain tuning with respect to thefresonantfre- .quency of a radial .cavityor cavities.

Stillkfurtherobjects oftheinvention will appear. as thedescription progresses, both by direct lrecitation thereof andby'implication `frornlthe context.

Referring to;tthe accompanying :drawing in which like numerals. of reference indicate-similar .parts throughout .thesseveral views;

Fig.. 1 .is a cross-sectional view, transverse -to the cathode, of a magnetron embodying the-present invention, taken on line I'I of Fig'. 2;

Fig'. 2 is a section longitudinal ofthe input and output leadsand on the plane including the cath- Fig Bis asectional'view at right angles to both Figs.. l. and 2 as on line III-III ofy Fig. 1;

' Fig; 4 isa sectional viewsimilar toFig. l-and vshowing a modified construction of tuning means;

and

LFig; 5 is a .similar I'sectional-view -showing-the f ymagnetron having `differently formed cavities from those of preceding gures.

, In the speciiic vembodiment of the invention i1- lustrated in said drawing, reference numeral I0 designates a cylindrical magnetron casing having end plates or covers II sealed thereto whereby the interior may be evacuated. Within the casing is a body portion or anode I2 of generally cylindrical shape,.shorter than the said casing and provided .with end flanges I3 for spacing the major parts of the ends of the anode or body portion from the endplates or covers I I and thereby afford the usual and necessary endspaces I4 within the magnetron. vIt is necessary for these flanges I3 to come quite closeto the cover plates II and for spacing or.. gap 21, sequently referred to between the casing. and body portion or anode, to be small to prevent the magnetic flux from passing between I.the shell or casing and the flanges and bodyportion. Such passage of flux, if permitted. would belikely to cause the magnetron to operate in spurious modes of operation.

The present showing of-magnetronpreferably 1 providesa cathode cavity vI5 parallel to but offset from or eccentric wthrespect to the axis of the anode body .and casing7 saidcavity extending through the body v,so as to open into both end spaces I4. Likewise eccentric to the anode body and extending therethrough to the end spaces are a plurality (here shown as two innumber) of cavity resonators .I6 which are otherwise separate `fromeach other but open longitudinally at the Y.side ofthe cathode cavity I5, as by constriction Extending through the cathode cavity vIE5 is a cathode IIJ-preferably coaxial tothe cavity and projecting into the end lspaces Ill. The cathode is supported at its ends by ceramic or other insulating collars I9 on the outer ends of which are mounted conductive discs 2U to which lead-in vwiresiZIyareradially attached. These lead-,in wires arey sealed through appropriate sealing .means 252 for the purpose at the side of thernagnetron. A heater filament 23 extends through the cathode and isattached at its ends to vsaid .discs 20. YAn output lead 2li is likewise shown vsealed through appropriate sealing means 25 at .the opposite side of the magnetron from the leadin wires. This output lead extendsin a radial direction forthe greater part of its length Within said end space, but has its inner end bent toward yand inserted in a hole for the purpose in the end face of the anode body. Preferably the said out- Vputlead overlies vthe portion ofthe anode body oiforming thegwallzbetween the eccentrically disposed cavity resonators I E. Longitudinally of the anode body also in the region of said wall between the cavities is provided a spacer support 26 by which the anode body is there rigidly mounted on the inner cylindrical face of the casing. Elsewhere between the anode and casing a spacing 21 is provided for permitting relative movement of the anode with respect to the casing.

It may now be observed that the eccentric cavity resonators I E arerelatively close to the outer wall of the anode at the part thereof next the side edges of spacer support 26, thereby constituting those parts of the anode resiliently movable regions 28. At the opposite side of the cathode cavity from said cavity resonators, the anode wall is longitudinally split, as at 29, with a gap between the faces forming the split sufficient to receive a stop strip 30 projecting from the casing into said gap.

By virtue of thev construction described, the anode body provides one fixed segment 3i projecting inwardly between the cavity resonators from the spacer support, and provides two other segments 32 at the other sides of said cavity resonators and which also extend around the cathode cavity as far as gap 29. These two segments 32 are symmetric with respect to each other and a plane centrally of the xed wall between the axes of the cavity resonators, said plane including the axis of the cathode cavity. Said two segments, while substantially rigid in themselves are movable toward and away from stop strip 39' by virtue of the resiliency of the thinned wall regions 28. Moving said segments alters the cavity resonator shape and capacity and changes the size of the constriction ll between the cavity resonators and the anode cavity. This obtains the desired tuning for wavelength. Stop strip 39 limits movement of the segment in the direction tending to close constrictions l? so that they cannot be closed entirely but are always open to passage of energy. Outward `swing of the segments is limited by engagement thereof with the inner face of the casing.

In order to control and manipulate the said anode segments, a separate control means is provided for each. Description of one will apply to both. At a mid-part of the cylindrical wall portion of the segment, a rod 33 projects outwardly through the casing. The inner end of said rod is shown threaded and permanently xed thereby in said segment. Around said rod coaxial therewith and sealed to the segment is a cylindrical housing 34. Within said housing is a flexible diaphragm 35 sealed to both the inside Wall of the housing and to the rod. Said rod projects beyond the diaphragm and housing and is threaded thereat, as indicated by numeral 36, to receive a knob-like cap 31 which has an outer iiange overlapping the end margin of the housing where threads 38 are provided of differential relation to threads on the rod whereby rotation of the cap effects a longitudinal displacement of the rod without the rod rotating. The construction accordingly enables either or both anode segments to be adjusted, making it possible to match the frequency of one cavity resonator to that of the other, and also to shift the frequency of the magnetron as a whole. A radio frequency quarter wave choke 39 is shown mounted on rod 33 within the evacuated portion of housing 34.

In accordance with showing of Figure 4, the invention is illustrated in conjunction with a magnetron wherein the casing and body or anode are unied and accordingly present no spacing for adjustment or tuning. The constlllftil shown comprises a magnetron body 40 having an eccentrically disposed cathode cavity 4| and eccentrically disposed cavity resonators 42 radiating from the cathode cavity. Radially from each of these cavity resonators extends a probe or rod 43, the outer structure and mounting of which conforms to the previously described structure and mounting for rod 33 with duplication of the longitudinal adjustment and flexible diaphragm sealing for said rod. Manipulation of the adjusting knob to move probe or rod so as to protrude more or less into the cavity resonator varies the capacity and thereby effects desired tuning over a considerable range. As in the previously described structure, independent adjustment is available to the two cavity resonators which again makes it possible to match the frequency of the one cavity resonator to that of the other and also to shift the frequency of the magnetron as a whole.

Figure 5 shows the invention applied to a magnetron having slot-like cavity resonators 44 in place of the conventional cylindrical ones. The same structure of adjustable probe or rod 43' as described above is utilized, as will be readily appreciated from the drawing.

The invention, irrespective of choice of embodiment, provides a means for varying the output wave-length over a considerable range of adjustment. Also, the cavity resonators may be separately tuned lso that assymetries in the resonators may be compensated by the matching. By virtue of this adaptability to matching the resonators, less accuracy in manufacture is required and greater tolerance for cathode mounting and eccentricity is acceptable. Both the matching feature and the fact the magnetron can be tuned as a whole not only makes it easier to manufacture within prescribed frequency limits, but enables the user to adjust and vary the frequency as found desirable or necessary. The eccentricity of the cathode cavity and consequent assymetry of the cavity resonators, with utilization of a restricted number thereof, lends itself to fulfillment of the desired matching and tuning as shown and described herein. Furthermore, the eccentricity of the cathode cavity and of the cavity resonators in the anode body is conducive to the construction of a magnetron of small size and for production of an output of short wave length.

Iclaim:

1. A magnetron having an anode body with a cathode cavity of fixed length therein and with a pair of other cavities each of which constitutes a cavity resonator of fixed length and laterally radiating from the cathode cavity, all of said cavities being longitudinally parallel and said pair of cavities having a common xed wall therebetween extending longitudinally of the cavity resonators, said pair of cavities having ad.- justable walls movable toward and away from said common fixed Wall by which the hollow volume of said cavity resonators is varied with the length thereof remaining constant for matching the frequencies of said cavity resonators, and a cathode in said cathode cavity,

2. A magnetron having an anode body with a cathode cavity of fixed length therein and with a pair of other cavities each of which constitutes a cavity resonator of Xed length and laterally radiating from the cathode cavity, all of said cavities being longitudinally parallel and said pair of cavities having a common wall therebetween extending longitudinally of the cavity resonators, a cathode in said cathode cavity, adjustable means for said resonant cavity resonators :comprisingadjustabiev'walls'movable'.ito- Ward and away fro'lnfsaidcommonfixediwalliby whichthe:hollowi-volumeiof said cavity resonators is varied with the length thereof remaining constant fori-'matching the'frequencies of said cavity resonators-and means atthe exterior of said anode body connected to -said vadjustable walls for moving said adjustable walls and effecting frequency" matching of said'cavity resonators.

3. Amagnetron having an `anode body'with a cathode cavity eccentrically-disposed therein and with cavity resonators eccentric `to the" anode body and radiating from the cathode cavitygthe diameter of fthe anode body lbeing coniined'to a size commensurate to the sum of the diameters of the cathode cavity and a single cavity resonator andthe cathode cavity andc'avityresonators beingmaximum in a-direction radial'to the cathode cavity commensurate tothe diameter of the anodebody thereby obtaining a magnetron of vminimum diameter fand cavities of maximum dimensionjin the available diametric size of Athe magnetron for production .of an output of short wave length, a -cathode in said `cathode cavity, and adjustable tuning controlmeans comprising adjustable'walls movable toward :and away-'from said common fixed wall by which the hollow volume of said cavity resonators is varied with the length thereof remaining constant for matching the frequency of said cavity resonators, and means at the exterior of said anode body connected to said movable walls for adjusting the same and tuning the cavity resonators to desired wave-length output.

4. A magnetron having an anode body with a cathode cavity eccentrically disposed therein and with two resonant cavities constituting cavity resonators eccentric to the anode body and on opposite sides of the axis of the anode body from the eccentrically disposed cathode cavity providing adjustable wall portions for the cavity resonators at the sides most remote from each other which said wall portions are also at the exterior of the anode body and each ,accessible to application from the exterior of tuning control means thereto, and tuning control means connected to each of said Wall portions for adjusting the resonant frequency of each of said cavity resonators.

5. A magnetron having an anode body with a cathode cavity eccentrically disposed therein and with two cavity resonators eccentric to the anode body and on opposite sides of the axis of the anode body from the eccentrically disposed cathode cavity thereby providing wall portions for the cavity resonators at the sides most remote from each other which said wall portions are also at the exterior of the anode body and each accessible to application from the exterior of tuning control means thereto, and tuning control means connected to each of said wall portions for adjusting the resonant frequency of each of said cavity resonators, said tuning control means protruding at opposite sides of the magnetron and iiexlbly sealed for movement toward and away from the anode.

6. A magnetron having an anode body with a cathode cavity and cathode therein and two cavity resonators radiating from the cathode cavity, tuning means for each of said cavity resonators, said tuning means comprising a rod projecting outwardly from said anode to the exterior of the magnetron and movable longitudinally of itself with respect to said magnetron, a radio frequency choke on each rod, and flexible means 7. A magnetron having v"ananode body with al cathode cavity andi cathode therein .and said body having-a splitfromione. partof said cavity to the outsidelof said body, said anode-having cavity Y`resonators vradiatingfrom said cathode cavityv onlthe .opposite side thereof from vsaid split, andadj-ustable tuning meansconn'ected 'to saidbody forsc'ompressing the anode'body and therebyvarying the sizeandltuning ofthe cavity resonators. v

8. A magnetron having an anodev body'with a cathodecavty one region whereof being closeto the exterior vof said body and said body having a split thereat, a cathode'in said cathode cavity, said anode 'having two cavity resonators radiating from fsaid cathode cavity on the opposite side thereof 'from said split, saidcavityresonators each having a region vclose to the exterior of said body and remotefrom the split in the anode, and adjustable tuning control means connected'to said bodyforflexing the-anode body atsaid regions of the cavityresonato'rs and thereby varying the size and tuning of the cavity resonators.

9. -A magnetronhaving an anode body with a cathode cavity and cathodetherein, with a split at one side of the cathode cavity and with two cavity resonators radiating from the cathode cavity at an opposite part thereof from said split, thereby forming the anode body in three segments, means rigidly mounting one segment, and adjustable tuning control means connected to said body for adjustably moving an adjacent segment and thereby varying the size of and tuning a, cavity resonator.

10. A magnetron having an anode body with a cathode cavity and cathode therein, with a, split at one side of the cathode cavity and with two cavity resonators radiating from the cathode cavity at an opposite part thereof from said split, thereby forming the anode body in three segments, means rigidly mounting the middle one of said segments, the two other of said segments being at opposite sides of the rigidly mounted segment, and adjustable tuning control means connected to each of said two other segments for adjustably moving the same and thereby varying the size of and tuning the cavity resonators.

11. A magnetron having an anode body with a cathode cavity, with a split at one side of the cathode cavity and with two cavity resonators radiating from the cathode cavity at an opposite part thereof from said split, thereby forming the anode body in three segments, means rigidly mounting one segment, another one of said segments being adjacent the rigidly mounted one, a rod carried by and protruding from said adjacent segment, adjustable tuning control means connected to said rod for adjustably moving said rod for adjusting said adjacent segment and tuning the magnetron, and a cathode in said cathode cavity.

12. A magnetron having a, sealed casing, an anode body in said casing, said anode body having a segment xed at its periphery to said casing, said anode body having two exible segments on opposite sides of said fixed segment and spaced from said casing, a cathode sealed within said casing, and adjustable tuning control means connected to said segments for ilexing the said two segments for tuning the magnetron.

13. A magnetron having a sealed casing, an anode body in said casing, said anode body having a segment fixed at its periphery to said casing, said anode body having two exible segments on opposite sides of said xed segment and spaced from said casing, a cathode in said casing, means for exing the said two segments for tuning the magnetron, said means comprising a rod of which one end is fixed to one of said two segments and the other end whereof projects from said casing, a housing projecting from said casing around said rod, and a knob-like cap threaded on said housing and rod for moving the rod longitudinally with respect to the housing.

14. A magnetron having a sealed casing and cathode within the casing, an anode body in said casing, said anode body having a segment xed at its periphery to said casing, and said anode body having two flexible segments on opposite sides of said fixed segment and spaced from said casing, and means for flexing the said two segments for tuning the magnetron, said means comprising a rod of which one end is fixed to one of said two segments and the other end whereof projects from said casing, a housing projecting from said casing around said rod, and a knob-like cap threaded on said housing and rod for moving the rod longitudinally with respect to the housing, and a exible diaphragm within the housing sealed theretoand 'to said rod eiecting a, vacnum-tight sealzfor the housing.

" ROBERT C. RETHERFORD.

REFERENCES CITED The following references are of record in the nie kof this patent:

- UNITED STATES PATENTS Number Name Date 2,408,234 Spencer Sept. 24, 1946 2,408,237 Spencer Sept. 24, 1946 2,348,986 Linder May 16, 1944 2,295,396 George Sept. 8, 1942 2,252,118 Dallenbach Aug. 12, 1941 2,115,521 Fritz et al. Apr. 26, 1938 2,163,589 Dallenbach June 27, 1939 2,323,729 Ryan July 6, 1943 2,157,952 Dallenbach May 9, 1939 2,270,777 Von Baeyer Jan. 20, 1942 2,063,342 Samuel Dec. 8, 1936 2,280,824 Hansen et al Apr. 28, 1942 2,167,201 Dallenbach July 25, 1939 FOREIGN PATENTS Number Country Date 215,600 Switzerland Oct. 16, 1941 

